Process of treating glyceride oils with activated magnesium oxide



Patented Nov. 30, 1948 PROCESS OF TREATING GLYCERIDE OILS WITH ACTIVATED'MAGNESIUM OXIDE Ralph A. Marmor, Deca- A. E. Staley Manufactur- WendellW. Moyer and tar, Ill., asslgnors to ing 00., Decatur,

111., a corporation of Delaware No Drawing. Application August 5, 1944Serial No. 548,304

The present invention relates to the refining of edible oils. Morespecifically, it pertains to the treatment of edible glyceride oils,having particular reference to improvements whereby reversioncharacteristics of such oils, as well as rancidity characteristics, areprevented, and the provision of a non-revertible, non-rancid oil, andprocess for producing the same, is a principal object of the invention.

More specifically, it is an object of the invention to remove fromglyceride oils, such as soybean oils, or the like, the impurity, orimpurities,

causing reversion characteristics to develop therein by subjecting suchoils to thorough mixing with activated magnesium oxide. 7

Yet more specifically, it is an object of the invention to treat crudeor purified edible glyceride oils, such as soybean .oils, or the like,with activated magnesium oxide and with activated carbon thereby toprevent the development of reversion characteristics as well asrancidity characteristics and to produce an edible oil therefrom whichwill not revert or become rancid even when stored for prolonged periodsof time.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

Present methods of refining edible glyceride oils are well known andneed no elaboration in detail. Briefly, however, the steps generallyinvolved consist of neutralization in which the oil is emulsified withcaustic soda solution and after the emulsion breaks the oil isseparated. It is then washed and dried. Thereafter it is bleached bymeans of small amounts of suitable adsorbents and preferably winterized.The final step is one of deodorization. Preferably, before and inconjunction with the deodorization step, however, the improvement of thepresent invention is practiced, although a purified oil up to this pointcan be substituted by a more or less crude oil as will more fully appearhereinafter.

The refining process briefly outlined above has for its objective theremoval of the undesirable accessory substances in the crude oil. Theneutralization and washing steps remove free fatty acids, phosphatides,sterol glucosides, some of the sterols, gums, and most of thenitrogenous compounds. Bleaching removes a considerable part of thecolor pigments and probably some colorless substances as well. Duringwinterization, which in the. case of soybean oil is unnecessary for thepurpose of removing saturated glycerides or stearines, a small quantityof in soluble material of unknown structure, possibly 7 Claims. (Cl.2.60427) a wax or sterol, separates and is removed by winter-pressing.During deodorization, practically all impurities which are volatile insteam at low pressures are removed.

Freshly refined soybean oil made from a crude oil derived from highgrade beans has a characteristic odor but is bland and sweet. It can beconsidered to be a high-class salad oil since the characteristic odor isnot objectionable. However, when heated to 425 F. in a so-called"cooking test, a sharp, .grassy odor develops. The chief drawback ofrefined soybean oil, however, is that in the course of from a few daysto months, depending upon conditions, the oil undergoes a peculiarchange which is known as reversion. This deterioration is accompanied bythe development of an undesirable odor and flavor which has beenvariously described as u s g y, D y, or y There is undoubtedly aprogressive change in odor and flavor, and the odor is not the same atthe beginning of the reversion period as toward the end. The process isnot true odor reversion because the odor does not revert to that ofeither the crude oil or the deodorized oil.

It should be observed that reversion and oxidative rancidity aredifferent, although possibly related, phenomena. Corn oil, one of thebest food oils, causes little trouble because of reversion but becomesrancid more rapidly than soybean oil as measured by peroxide formation.

Attempts to correlate soybean oil' reversion with peroxide values havenot led to fruitful results. A tremendous amount of research effort hasr been expended in attempting to prevent soybean oil reversion and todetermine the underlying cause. The theory that has attracted thelargest following in recent years is that soybean oil reversion is dueto the presence of a small percentage of linolenic acid, an unsaturatedfatty acid containing three double bonds, in the glyceride molecules.Corn and cottonseed oil, whichare not subject to much reversion, do notcontain a detectable amount of linolenic acid. On the other hand,linseed oil which contains a high percentage of linolenic acid ischaracterized by a typical, strong painty odor. According to thistheory, the linoleic acid decomposes in storage to odoriferoussubstances because of oxidation with air, condensation, ring closure, orsome unknown kind of reaction.

On this assumption work on the reversion problem has been directedtoward the eliminathis case to remove the linolenic acid by hydrolysisof the glycerides and separation of the fatty acids, the main lineofattack has been partially and selectively to hydrogenate the oil withthe objective of converting the linolenic acid to a more saturated acidsuch as linoleic. Unfortunately, the partial hydrogenation has not beenamenable to selective control with the result that stearines and solidisomeric unsaturated acids are formed to an undesirable extent.Furthermore, reversion is not entirely prevented and the oil acquires inaddition a "gassy odor.

It would seem that reversion is due'to the presence of minute quantitiesof impurities or accessory substances that have not been removed in therefining process. In particular, nitrogenous impurities, likephosphatides or fragments thereof, slowly decompose on standing to yieldamines having a penetrating and objectionable odor. The fact thatrefined soybean oil made from first grade beans is more stable than thatmade from beans containing frost and fielddamaged beans indicates thatreversion may be caused by residual impurities in the refined oil. Theseimpurities cannot completely be removed by conventional refiningmethods.

The invention herein disclosed was, in effect, the accidental outgrowthof a fundamental study on the chromatographic adsorption of the coloredaccessory compounds in soybean oil. In this work soybean oil dissolvedin hexane was passed through a glass column uniformly packed with alight-colored adsorbent agent. When using magnesium oxide as theadsorbent material, the colored materials in the oil were selectivelyadsorbed. The most strongly adsorbed pigment was adsorbed first, thenext strongly adsorbed material was then adsorbed and so on, until, atthe end of the pass, the adsorbent material was colored by a series ofbands; of pigments of different colors. Each band represented adifierent pigment or mixture of pigments. The bands were spread apartand the edges sharpened .by passing more solvent through the column.Then, by pushing out the column material, the bands were separatedmechanically and the adsorbed material in each band studied separately.It was seen that magnesium oxide had adsorbed green chlorophyll morestrongly than the yellow and red pigments. All of the green pigmentformed a tight green band at the top of the column.

The green band adsorbed on magnesium oxide was removed from the columnand the adsorbed material extracted with solvents. It gave a positivetest for chlorophyll. After removal of solvents it was noted that thegreasy residue had a strong, unpleasant odor, resembling that of a badlyreverted soybean oil. An, impurity responsible for the reversion ofsoybean. oil was thus removed by the magnesium oxide. The oil passedthrough the magnesia column was then treated to remove solvent andstored in corked glass bottles in diffused daylight for a long period oftime. It did not revert.

It later was developed that a solvent such as hexane was unnecessary andthat the oil could be eflectively treated simply by agitating withtheproper amount of activated magnesia under suitable conditions, andthen filtering off the magnesia.

The effectiveness of this treatment depends upon the removal byselective adsorption on the magnesia of some impurity or impuritieswhich cause reversion. By the present invention substances apparentlyare removed which directly decompose or oxidize to products havingdisagreeable odors and flavors, or substances having a catalytic effecton the decomposition of otherwise stable accessory substances, orunsaturated glyceride molecules are removed. The chlorophyll substancesalso may be the cause of reversion, or the revertible substances may beremoved simultaneously with the chlorophyll. In

any event, the impurities, or those substances responsible for thereversion characteristics, were removed with the removal of thechlorophyll.

In practicing the present invention the following controlled operatingconditions cover preferred operating ranges for treating a glyceride oilwith activated magnesium oxide:

Temperature 20-150" 0. (preferred 40 to Time 2-4 hours Quantity of MgO0.1 to 6.0% (based on oil) Pressure Normal or sub-atmospheric Anytemperature up to 150 C. gives acceptable results. Above 150 C. somediscoloration of the oil occurs and the oil is liable to oxidation.Since the selectivity of the adsorption on magnesia is not increased byhigher temperatures and is just as effective at ordinary temperatures,it is preferable to work in a range of 40 to 60 C.

The time of treatment is not independent of the other factors but ispartially dependent upon the quality of the starting oil and thequantity and activity of the magnesia used. A treatment period of from 2to 4 hours is preferred.

The quantity of magnesia to be used also is not-an independent variablebut depends on the activity of the magnesia and the kind of startingoil. When starting with an alkali-neutralized, washed, dried, bleachedand winterized oil, only about 0.5 per cent of an activated magnesia isrequired. When starting with a neutralized, washed and dried oil of thesame stock, from 2.5 to 3 percent of the same grade of magnesia isrequired for effective treatment. In treating an oil having a greatertendency to revert than soybean oil, such as linseed oil, it isnecessary to use a larger amount of magnesia, in the range of from 3 to6 per cent. Oils such as cottonseed and corn which are subject to butlittle reversion, can be I Either a powdered or granular type of ,acti"vated magnesia can be used. Pelleted, activated magnesia from the powderwould be acceptable. A granular or pelleted form of magnesium oxide ispreferred because of ease of filtration.

Ordinary magnesium oxide purchased on the market is inactive and doesnot have any selective adsorption properties. However, the same'material can be activated by heating with water to about C., forapproximately one hour, filtering, drying and heating in the range of350 to 500 C. for 3 hours or longer. Commercial products also areavailable.

Preferably, the oil is put-through the initial steps of the conventionalrefining process which includes alkali-neutralization, washing and drytostart with crude tion is applicable to ing. In certain cases it may beadvantageous oil and employ a larger quantity oi magnesia, but in mostcases it is better partially to purify the oil before treatment. In casethe crude oil is particularly poor in quality, the best results areobtained by bleaching the oil in the regular manner with bleachingearths before treating with magnesia. Although deodorized oil may beused, it is preferable to 101- low the magnesia treatment with tionstep.

The magnesia treatment of the present invenall types of revertibieglyceride oils including vegetable, animal and marine oils. As anextreme example, linseed oil which is but seldom used for ediblepurpose, can be rendered sweet and non-reverting by the magnesiatreatment when followed by deodorization. Fish oils, such as sardine andpilchard oils, are remarkably improved so far as odor and flavor areconcerned.

the deodoriza- Example 1 The magnesia treatment was carried out in avacuum-tight steel vessel equipped with heating and cooling coils and atwo-bladed agitator. Ad-

-ditional equipment included plate and frame presses, storage andtransfer tanks, pumps and a deodorizer.

One barrel of neutralized, washed, dried and bleached soybean oil, 418lbs., was pumped into the vessel and to this wasadded 2.1 lbs. (0.5 percent) of magnesia. The stirrer was started and the vessel evacuated toabout 20 mm. Hg pressure. The oil was warmed to about 48 C. and stirredfor 3 hours. The charge was then pumped to a tank and mixed with 2gallons of filter aid. The oil was then pumped to a filter press andfiltered through paper, recycling until. the filtrate was clean. Thefiltered oil was then pumped to the deodorizer and treated with steamunder high vacuum under conditions identical with those used in makingordinary edible soybean oil.

was clear yellow in appearance. n the Lovibond scale the color was20Y-2.3R. The flavor was extremely bland and sweet. It had a very faint,pleasant odor. Particularly noteworthy was the odor when the oil washeated F. in the cooking test. The strong, grassy odor of soybean oildid not evolve although a faint sharp odor could be detected.

.Ezample 2 A sample of crude linseed oil was neutralized, washed anddried by the process similar to that the oil deodorized by vacuum steamdistillation in the regular manner. The resulting oil was free of fishyor painty odors and remained that way upon storage.

By means of the present invention a tremendously increased supply of hias corn and cottonseed oils, which until now have been considered to bethe premium domestic edible oils. An edible grade of linseed oil, whichheretofore has been considered entirely unsuitable for edible purposes,due to objectionable odor and flavor, can be produced at small extraexpense. Marine oils, which at best are not particul'arly adapted foredible purposes, can almost completely be deodorlzed.

The magnesia treatment in the case of marine oils does not, however,prevent the facile polymerization or drying of these oils, anundesirable property infood oils. Edible oils, such as corn, cottonseedand olive oils, can be further improved in flavor and color by magnesiatreatment.

The invention hasmany outstanding advantages. For example, it can bepracticed under the mildest conditions as an adjunct of an establishedprocess for refining edible oils. The nature and conditions are suchthat undesirable side the oil, Y (In processes involving partialhydrogenation, the chemical nature of the oil is changed with theprobable formation of unnatural isomers and iso or geometric isomers ofsome of the unsaturated fatty acid radicals.) The magnesia process notonly prevents reversion, but also removes substances which give edibleoils an undesirable appearance. At the same removed when using thequantity of magnesia required to prevent reversion.

Soybean oil, which has been rendered nonrevertible by treatment withactivated magnesia, has been found to develo upon storage, a more rpronounced tendency toward oxidative rancidity,

as measured by increase in peroxide content, than either unrefinedsoybean oil or oil that has een refined by conventional methods.

ment of oxidative rancidity.

In the process for producing the oil, we prefer to treat the oil with amixture of magnesiaand Example 3 To 70,900 lbs. of neutralized, washedand dried soybean oil in a large kettle equipped with an dativerancidity.

which embody the invention may be made without 7 departing from itsscope. it is intended that all matter contained in the above descriptionor shown in the accompanying drawing shah be interpreted as illustrativeand not in a" limiting sense. t

It is also to be understood that the followin claims are intended tocover all of the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention which, as amatter of language, might be said to fall therebetween.

Having described our invention, what we claim as new and desire tosecure by LettersPatent is:

1. The process of treating glyceride oil, which comprises mixing saidoil with activated magnesium oxide prepared by heating hydratedmagnesium oxide for about three hours at a temperature lying within therange of about 350 C. to

about 500 C. to stabilize the oil against reversion characteristics, andthereafter separatingsaid oil from said magnesium oxide.

2. The process of treating soybean oil, which comprises intimatelymixing said oil with activated adsorbent magnesium oxide prepared byheating hydrated magnesium oxide for about three hours at a temperaturelying within the range of about 350 C. to about 500 C. to removeimpurities which cause reversion characteristics to develop in said oil,filtering said mixture to separate said oil from said magnesium oxide,and then deodorizing said oil.

3. The process of treating glyceride oils adsorptively to removeimpurities which cause reversion characteristics to develop therein,which comprises adding to said oil approximately 0.1 to 6.0 per cent ofactivated adsorbent magnesium oxide prepared by heating hydratedmagnesium oxide for about three hours at a temperature lying within therange of about 350 C, to about 500 C. based on the weight of'the oil,and thoroughly mixing said oil and said oxide until the latter hasadsorbed those impurities present in said 011 which normally cause saidreversion characteristics to develop.

4. The process of treating glyceride oils adsorptively to removeimpurities which cause reversion characteristics to develop therein,which comprises adding to said oil approximately 0.1 to 6.0 per cent ofactivated adsorbent magnesium oxide prepared by heating hydratedmagnesium oxide for about three hours at a temperature lying within therange of about 350 C. to about 500 C,

based on the weight of the oil, and thoroughly mixing said oil and saidoxide under the combined action of heat and sub-atmospheric pressureuntil said oxide has adsorbed those impurities present in said oil whichnormally cause said v reversion characteristics to develop,

5. In the production of refined edible glyceride oil, the improvementwhich comprises subjecting said oil to treatment with an activatedadsorbent magnesium oxide prepared by heating hydrated magnesium oxidefor about three hours at a temperature lying within the range of about350 C. to about 500 C. by thoroughly mixing them together, and removingfrom said oil, by the removal of said magnesium oxide, adsorbedimpurities which cause the development of reversion characteristics insaid oil.

6. The process of mixing vegetable oils with magnesium oxide prepared byheating hydrated? magnesium oxide for about three hours at a temperaturelying within the range of about 350 C. to about 500 C. to preventreversion.

'7. The process of contacting vegetable oils with activated magnesiumoxide prepared by heating hydrated magnesium oxide for about three hoursat a temperature lying within the range of about 350 C. to about 500 C.mixed with activated carbon to prevent reversion and rancidity.

WENDELL W. MOYER. RALPH A. MARMOR.

REFERENCES CETED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date Hood June 28, 1910 Buxton Aug. 31, 1943FOREIGN PATENTS Country Date Great Britain July 27, 1883 OTHERREFERENCES Number Number

